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97 o                               Appendix V.

|rf                                                             CHAPTER III.

i|;:,                              P. 86. Soldering is the process of uniting metals by readily

k\<*                          fusible alloys that melt at temperatures that do not injure the

^| |                         work.    The methods may be classed under hard soldering and

', 1 I                         soft soldering.    The former, called also brazing, already described

F | j i                        at p. 86, requires a temperature of 500° F. or more.    Soft solder

! !' L                        consists of 3 parts by weight of lead to 2 of tin, melting at about

||*f                         340° F., and a flux of * killed spirit' may be used to clean the

f|J                         joint and prevent oxidation.    This flux is obtained by dissolving

jt'"j-                        scraps of zinc in hydrochloric acid till the latter is completely

^j ,j                         changed to zinc sulphate, when an equal quantity of water is

added. It is objectionable as causing rust, so in many cases, as
in electric wiring, it is not permissible, resin only being allowed,
to which a little oil may be added; but as resin does not clean
the joint, the parts must be thoroughly rubbed and scraped
before soldering. The soldering bit, made of copper, must also
be cleaned and ' tinned' with solder before commencement. Soft
soldering, when applied to unite bearing brasses and the like, is
often termed ' sweating.'


P. 95 &* 282. Rivet Making.—Vincent's machine for heading
bolts and rivets, shewn in Fig. 9020, is much in favour on
account of the excellent work produced by it. A standard A
carries in bearings B B a shaft c, which is rotated from a counter-
shaft by the pulley D. Upon c are fixed two bevel friction* wheels
E and F, that alternately drive the third friction wheel G placed on:
the vertical screw shaft H. The coarse-pitched screw H carries
an upper die j, which remains at a constant height, and also
gives vertical motion to the tup K, which travels between the
slides L L on the frame A. This tup is in one piece with the
lower die M, into which is inserted the hot rivet shank; and the
depth of the hole to receive the latter is decided by the position
of the buffer nut N, which may be raised or lowered and then
fixed by the screw clamp lever p. The shaft c is pressed leftward
by the weight Q and bell-crank R bearing on the shaft end, and a